Chen Yi-Hao, Wise Frank
School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
APL Photonics. 2024 Mar 1;9(3):030902. doi: 10.1063/5.0189749. Epub 2024 Mar 14.
Raman scattering has found renewed interest owing to the development of gas-filled hollow-core fibers, which constitute a unique platform for exploration of novel ultrafast nonlinear phenomena beyond conventional solid-core-fiber and free-space systems. Much progress has been made through models for particular interaction regimes, which are delineated by the relation of the excitation pulse duration to the time scales of the Raman response. However, current experimental settings are not limited to one regime, prompting the need for tools spanning multiple regimes. Here, we present a theoretical framework that accomplishes this goal. The theory allows us to review recent progress with a fresh perspective, makes new connections between distinct temporal regimes of Raman scattering, and reveals new degrees of freedom for controlling Raman physics. Specific topics that are addressed include transient Raman gain, the interplay of electronic and Raman nonlinearities in short-pulse propagation, and interactions of short pulses mediated by phonon waves. The theoretical model also accommodates vector effects, which have been largely neglected in prior works on Raman scattering in gases. The polarization dependence of transient Raman gain and vector effects on pulse interactions via phonon waves is investigated with the model. Throughout this Perspective, theoretical results are compared to the results of realistic numerical simulations. The numerical code that implements the new theory is freely available. We hope that the unified theoretical framework and numerical tool described here will accelerate the exploration of new Raman-scattering phenomena and enable new applications.
由于充气空心光纤的发展，拉曼散射重新引起了人们的兴趣，充气空心光纤构成了一个独特的平台，用于探索超越传统实心光纤和自由空间系统的新型超快非线性现象。通过针对特定相互作用机制的模型已经取得了很大进展，这些机制由激发脉冲持续时间与拉曼响应时间尺度的关系来界定。然而，当前的实验设置并不局限于一种机制，这就促使需要跨越多种机制的工具。在此，我们提出了一个实现这一目标的理论框架。该理论使我们能够以全新的视角审视近期的进展，在拉曼散射的不同时间机制之间建立新的联系，并揭示控制拉曼物理的新自由度。所涉及的具体主题包括瞬态拉曼增益、短脉冲传播中电子和拉曼非线性的相互作用以及由声子波介导的短脉冲相互作用。该理论模型还考虑了矢量效应，而在先前关于气体中拉曼散射的研究中，矢量效应在很大程度上被忽视了。利用该模型研究了瞬态拉曼增益的偏振依赖性以及矢量效应通过声子波对脉冲相互作用的影响。在这篇综述文章中，将理论结果与实际数值模拟结果进行了比较。实现新理论的数值代码可免费获取。我们希望这里描述的统一理论框架和数值工具将加速对新拉曼散射现象的探索，并实现新的应用。
